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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

42942 results found.

  1. GRB 260127A: GECAM-B observation
  2. GRB 260131A: NOT spectroscopic redshift z = 1.434
  3. EP260131a: Liverpool Telescope optical upper limits
  4. EP260131a: COLIBRÍ further observations
  5. Konus-Wind detection of GRB 260128A / EP260128a
  6. GRB 260131A: Insight-HXMT/HE detection
  7. Konus-Wind detection of GRB 260131A/B
  8. EP260131a: SVOM/VT optical observation
  9. EP260131a: Xinglong optical upper limit
  10. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  11. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  12. GRB 260131A/B: Fermi GBM Observation
  13. EP260131a: COLIBRÍ observations of slow optical fading
  14. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  15. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  16. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  17. GRB 260131B: MAXI/GSC detection
  18. GRB 260131A: Fermi GBM Final Real-time Localization
  19. EP260131a: COLIBRÍ optical observations of the counterpart
  20. EP260131a: Las Cumbres detection of an optical counterpart
  21. GRB 260127B: AstroSat CZTI detection
  22. GRB 260130A: Fermi GBM Detection
  23. EP260131a: Einstein Probe detection of an X-ray transient
  24. GRB 260127B: Fermi GBM Detection
  25. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  26. Fermi GRB 260130A: Global MASTER-Net observations report
  27. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  28. GRB 260130A: Fermi GBM Final Real-time Localization
  29. Fermi GRB 260129A: Global MASTER-Net observations report
  30. GRB 260128B: LCO optical upper limits
  31. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  32. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  33. IPN triangulation of GRB 260121A
  34. GRB 260127A: Swift-BAT refined analysis
  35. GRB 260129B: Fermi GBM Final Localization
  36. GRB 260128B: SVOM detection of a burst through offline search
  37. GRB 260129A: Fermi GBM Final Localization
  38. IPN triangulation of GRB 260127B (short)
  39. GRB 260127B: Swift-XRT observations
  40. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  41. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  42. EP260128a: NOT optical counterpart candidate
  43. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  44. EP260128a: Liverpool Telescope optical observations and possible counterpart
  45. EP260128a: LCO optical upper limits
  46. EP260126a: SVOM/VT optical upperlimit
  47. EP260128a: Global MASTER-Net observations report
  48. EP260128a: Einstein Probe detection of an X-ray transient
  49. Fermi GRB 260127A: Global MASTER-Net observations report
  50. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  51. GRB 260127A: Fermi GBM Observation
  52. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  53. GRB 260127A: COLIBRÍ optical observations
  54. GRB 260127A: NOT optical observations
  55. GRB 260127B: Swift ToO observations
  56. EP260126a: Seimei/TriCCS optical upper limit
  57. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  58. GRB 260127A: Swift-XRT refined Analysis
  59. GRB 260127B: GOTO candidate optical counterpart
  60. GRB 260127A: SVOM/C-GFT optical observations
  61. The EP-WXT trigger 01709253145 is likely a flaring star
  62. GRB 260127A: Enhanced Swift-XRT position
  63. Fermi GRB 260127B: Global MASTER-Net observations report
  64. GRB 260127B: Fermi GBM Final Real-time Localization
  65. GRB 260127A: Prompt enhanced Swift-XRT position
  66. Swift GRB 260127A: Global MASTER-Net observations report
  67. GRB 260127A: LCO optical afterglow discovery
  68. GRB 260127A: Swift detection of a burst
  69. GRB 260127A: Fermi GBM Final Real-time Localization
  70. GRB 260125A: Swift-XRT observations
  71. EP260126a: EP-FXT follow-up observation
  72. EP260126a: Optical upper limit with Kinder observations
  73. EP260126a: Liverpool Telescope optical upper limits
  74. EP260126a: Further NOT optical upper limits
  75. EP260126a: COLIBRÍ optical upper limits
  76. EP260126a: NOT optical observations
  77. EP260126a: Einstein Probe detection of a fast X-ray transient
  78. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  79. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  80. Konus-Wind detection of GRB 260120B
  81. GRB 251222A: SVOM/ECLAIRs refined analysis
  82. GRB 260125A: Swift ToO observations
  83. GRB 260125A: GOTO candidate optical counterpart
  84. Fermi GRB 260125B: Global MASTER-Net observations report
  85. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  86. GRB 260125B: Fermi GBM Final Real-time Localization
  87. GRB 260125A: Fermi GBM Final Real-time Localization
  88. GRB 260114A: SVOM/VT optical upper limits
  89. GRB 260120A: AstroSat CZTI detection
  90. GRB 260122B: Swift-BAT refined analysis
  91. GRB 260120B: SVOM/GRM observation
  92. GRB 260120A: GECAM-B observation
  93. GRB 260120B: AstroSat CZTI detection
  94. GRB 260114A: Insight-HXMT/HE detection
  95. GRB 260122B: Swift detection of a burst
  96. Swift GRB260122.97: Global MASTER-Net observations report
  97. EP260119a: Assy AZT-20 optical observations
  98. EP260119a: Mondy and SAO RAS optical upper limits
  99. GRB 260122A: Fermi GBM Final Real-time Localization
  100. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility

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